The condition is startling, but in dealing with such subjects we must be prepared to meet with anomalies. They come, as the ghosts appeared to Odysseus in Hades, at first one by one, then in an awe-inspiring swarm. Yet, in spite of the perplexities they occasion, we can discern, with growing sureness of insight, the amazing reality of the universal medium. It is, in a manner, the only reality. For what is manifest to sense is subject to change. We can conceive that the visible framework of material existence might crumble and dissolve, like 'the baseless fabric of a vision,' into seeming nothingness. But a substance that is inapprehensible is, to our limited ideas, imperishable. The ether is assuredly the seat of intense activities, which lie at the root, most likely, of all the processes in Nature. An absolutely uniform medium, however, can scarcely be imagined to energize or react. Some kind of heterogeneity it must possess; and the heterogeneity produced, in Dr. Larmor's view, by strains, is associated, in Professor Reynolds's theory, with intrinsic texture. The 'Sub-Mechanics of the Universe' are here made to depend upon the fitting together of ineffably small, ideally rigid grains. A misfit gives rise to matter, which might hence be defined as 'ether out of joint'; and the misfit can be propagated endlessly from one range of granules to the next. This propagation through the ether of an abnormal arrangement of its constituent particles, without any transference of the particles themselves, explains the phenomena of matter in motion. A concrete existence belongs to the ether alone. It is composed of round aboriginal atoms, the diameters of which measure the _seven hundred thousand millionth part_ of the wave-length of violet light.[81] They are packed closely together, yet not so closely but that free paths are left to them averaging in length the _four hundred thousand millionth part_ of their diameters. This inconceivably small relative motion suffices, nevertheless, to render the medium elastic; is, indeed, 'the only cause of elasticity in the universe, and hence is the prime cause of the elasticity of matter.' The medium so formed is ten thousand times denser than water; it exerts a mean pressure of 750,000 tons on the square inch; the coefficient of its transverse elasticity is 9 + 10^{24} (in C.G.S. units); which gives a velocity of transmission identical with that of light for vibrations of the same type, while longitudinal waves are propagated 2·4 times more rapidly. The scheme further includes a plausible rationale of gravity and of electrical effects; so that there is much to warrant the claim of its author to have excogitated 'the one and only conceivable purely mechanical system capable of accounting for all the physical evidence, as we know it, in the universe.'